Introducing their work, Son et al. (2014) write that "although many studies have addressed the impact of temperature on mortality, relatively fewer studies have evaluated the effects of temperature on morbidity outcome, such as hospital admissions," which knowledge, they say, " is needed to understand the full scope of weather's impacts on health." And in light of the dearth of such knowledge, they describe what they learned about this phenomenon in eight cities in Korea.

Working with hospital admissions data from eight major Korean cities (Seoul, Busan, Incheon, Daegu, Daejeon, Gwangju, Ulsan and Jeju) -- covering the period between 1 January 2003 and 31 December 2008, which data they obtained from the National Health Insurance Corporation of the Republic of Korea -- the three researchers made a number of interesting discoveries. First of all, they found that the association of heat with hospital admissions was the highest on the same day or days of the heat (lag 0 days), while the cold-related risk of hospitalizations lasted for longer time periods (lag 0-32 days). And not surprisingly, therefore, they concluded that "cold effects generally appear higher than heat effects in most cities," further citing the confirmatory results of the studies of Braga et al. (2001), Hajat and Haines (2002), Schwartz et al. (2004), Anderson and Bell (2009), Green et al. (2010), and Son et al. (2011).

Last of all, they report that the overall heat effect for cardiovascular hospitalization was but a modest 4.5% increase in risk when comparing hospitalizations at 25°C to 15°C, while they say they did not find any "statistically significant effects of heat waves compared with non-heatwave days." In other words, although the cardiovascular hospitalization rate slightly increased as the temperature rose in general, temperature extremes from heat waves had no discernible impact. On the other hand, with respect to the effect of cold weather, they authors report there were very significant increases in hospitalizations when comparing the admissions at 2°C with those at 15°C, which increases amounted to 50.5%, 43.6 % and 53.6% for allergic diseases, asthma, and selected respiratory diseases, respectively.

Clearly, a little global warming could do a lot to reduce health-related hospitalizations of metropolitan living Koreans.

Hajat, S. and Haines, A. 2002. Associations of cold temperatures with GP consultations for respiratory and cardiovascular disease among the elderly in London. International Journal of Epidemiology31: 826-830.